<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .line-height .one {
            line-height: 40px;
            font-size: 16px;
        }
    </style>
</head>

<body>
    <div class="line-height">
        <div>
            上面行
        </div>
        <div class="one">
            中间行
        </div>
        <div>
            下面行
        </div>
    </div>
</body>

</html>